Inferring mental operations from reaction-time data:
How we compare objects

"The study of the time relations of mental phenomena is important from
several points of view: it serves as an index of mental complexity,
giving the sanction of objective demonstration to the results of
subjective observation; it indicates a mode of analysis of the simpler
mental acts, as well as the relation of these laboratory products to
the processes of daily life; it demonstrates the close inter-relation
of psychological with physiological facts, an analysis of the former
being indispensable to the right comprehension of the latter; it
suggests means of lightening and shortening mental operations, and thus
offers a mode of improving educational methods; and it promises in
various directions to deepen and widen our knowledge of those processes
by the complication and elaboration of which our mental life is so
wonderfully built up."